This proposal describes an investigation of the cellular neuronal mechanisms that mediate behavior. The effector systems to be studied are the ink gland and the cardiovascular system of the marine snail Aplysia. Behavioral and intracellular electrophysiological techniques will be employed. Particular emphasis will be placed on analyzing the mechanisms underlying stereotyped behavioral responses. An attempt will be made to analyze both cellular membrane biophysical and biochemical properties of nerve and muscle cells, as well as intercellular features of neural control systems. The interaction of hormones with the nervous system will also be examined.